‘Tae 
et oid 
443 
- 
oxide was decomposed. ‘The tube was then introduced into the bath and 
heated continuously, except that at the end of each day it was removed 
and the diphenylamine renewed. After being replaced in the bath the 
pressure always returned at once to its previous value, thus showing that 
during the rapid cooling and heating the reaction had not proceeded to 
any appreciable extent. During the experiment the temperature varied, 
chiefly on account of the gradual decomposition of the diphenylamine, 
between the 301.5° and 303°. We may take 302° as the average tem- 
perature. It may be noted here that 1° difference in temperature makes 
a difference in pressure of a little less than half an atmosphere. 
The first experiment was made with sample B of the oxide. After 
being inclosed in the tube it was heated gently with a Bunsen flame until 
white spots began to appear in it. It was then introduced into the bath, 
the manometer indicating 6 atmospheres. At the end of two days the 
pressure had reached 16.7 atmospheres and was increasing very slowly. 
The tube was then removed from the bath and heated until a little more 
of the oxide was decomposed. When replaced in the bath the pressure 
was 20.2 atmospheres. During the next twenty-four hours the pressure 
remained constant at this point within one-tenth of an atmosphere. The 
tube was again removed and heated until, on being replaced, 23.2 atmo- 
spheres was registered. In the next twenty-four hours this pressure fell 
to 21.6 and in twenty-four hours more to 21.5 atmospheres. 
This experiment shows that the decomposition pressure at 302° must 
be considerably above 16.7 atmospheres (contrary to the conclusions of 
LeChatelier, who placed it between 10 and 15 atmospheres), it is probably 
not far from 20.2 and it certainly is not greater than,21.5. 
The experiment was then repeated with another tube containing the 
same kind of oxide. In this case a longer time was allowed for equili- 
brium to become established. Table IIT shows the pressure at the end of 
each twenty-four hours. 
TABLE ITI. 
Time in days. Pressure in atmospheres. 
1 Lek 
15.1 
17.3 
18.8 
19.5 
19.7 
19.7 
19.7 
aAaNanrk Ww DY 
It is evident from these two experiments that the correct pressure 
must lie between 19.7 and 21.5, and probably nearer to the former value 
than to the latter. Let us take 20.5 as a value sufficiently exact for our 
purposes. 
